Aquifer Thermal Energy Storage (ATES) systems provide sustainable space heating and cooling for buildings. In future, many buildings in moderate climates rely on ATES for their space heating and cooling. However, the subsurface space available for heat storage is limited and, there is a trade-off between individual ATES system efficiency and minimizing greenhouse gas emissions in an area by facilitating as much ATES systems as possible. Therefore, is it important to explore how aquifers can be utilized sustainably and to its full potential to maximize energy saving with ATES. In this dissertation methods for design, governance and planning of ATES systems in busy areas are presented. It is also identified where in the world suitable aquifers and climatic conditions coincide with urban areas; the future hot-spots for ATES, where these methods are needed.The presented design methods result in more efficient use of the subsurface and lower heat losses during storage for individual systems. The results also show that in areas with many buildings with ATES, the developed mathods for governacne and planning of ATES wells result in much larger energy savings by sustainably accommodating more ATES system than is done and allowed in current practice.